| 摘要 |
PURPOSE:To control the capacitance within the same substrate without any external power supply circuit by changing an output of the voltage boost circuit through the variable voltage selection circuit and by applying such outputs to the semiconductor variable capacitance element. CONSTITUTION:A capacitance variable circuit comprises the semiconductor variable capacitance element 16, control circuit 9, voltage boost circuit 10 and variable voltage switching circuit 11. From the circuit 9, a voltage boost clock 12a and voltage boost circuit stop signal 12b are output from and these are applied to the circuit 10. The variable voltage selection signal 13a and capacitance variable signal 13b output from the circuit 9 are applied to the circuit 11. A boosted output 14 of circuit 10 is sent to the circuit 11. An output 15 of the circuit 11 is input to the element 16. A capacitance of element 16 can be increased or decreased without using an external power supply circuit by selecting an output of the circuit 10 with the circuit 11 and supplying it to the capacitance variable terminal and the power supply terminal of the element 16. |
